The operation of the polyol pathway is being studied in normal and diabetic animal lenses as well as in post-operative human lenses. Studies conducted so far indicate that the development of diabetic cataracts in most animals is because of an accumulation of excessive sorbitol in the lens. The synthesis of sorbitol is incumbent to tissue aldose reductase activity and the concentrations of various cofactors such as NADPH and NAD. It is also incumbent upon the activity of the key enzymes of glycolytic pathway and of hexomonophosphate pathway. Studies on these lines are being extended to higher animals so that the implications of aldose reductase can be examined in reference to the etiology of cataracts in human diabetics. In continuation of this, lenses extracted from human diabetics and normal persons are being examined for the levels of sugars and polyols and the various enzyme levels. Biometric study is being conducted to assess the relationship between the refractive changes accompanying diabetes in animals and activity therein of aldose reductase. These experiments will yield information useful for evaluating the efficacy of aldose reductase inhibitors in fluctuations of vision in early diabetes and subsequent development of cataracts. New compounds are being screened in order to improve the potency and pharmacological suitability of aldose reductase inhibitors.